Balloon construction



1964 w. c. BORGESON ETAL 3,

BALLOON CQNSTRUCTION 4 Sheets-Sheet 1 Filed Sept 23 1960 Om mm Om mm INVENTORS WESLEY C. BORGESON HARVEY E. HENJUM BY GORDON R. WHlTNAH fiza 5. M

ATTORNEY 1964 w. c. BORGESON ErAL 3,119Q579 BALLOON CONSTRUCTION Filed Sept. 25, 1960 4 Sheets-Sheet 2 INVENTORS' WESLEY C. BORGESON HARVEY E. HENJUM GORDON R. WHITNAH zzzamww ATTORNEY Jan. 28, 1964 w. c. BORGESON ETAL 3,119,579

BALLOON CONSTRUCTION Filed Sept. 1960 4 Sheets-Shee t 5 I30 I28 IG. |22 |40 1... I26 I42 IN VEN TORS WESLEY C. BORGESON HARVEY E. HENJUM GORDON R. WHITNAH ATTORNEY 1964 w. c. BORGESON ETAL 79 BALLOON CONSTRUCTION Filed Sept. 23, 1960 4 Sheets-Sheet 4 INVENTORS WESLEY C. BORGESON HARVEY -E. HENJUM GORDON R. WHITNAH ATTORNEY United States Patent 3,119,579 BALLOON (IONSTRUCTHON Wesley L. Borgeson, Harvey E. Henjurn, and Gordon R.

Whituah, Minneapolis, Minn., assignors, by mesne assignments, to Litton Systems, Inc Beverly Hills, Calif a corperation of Maryland Filed Sept. 23, 1960, Ser. No. 57,933 17 Claims. (Cl. 244-31) The present invention relates to balloons, and more particularly to aerodynamically shaped balloons having a substantially constant volume gas envelope, means for maintaining a predetermined pressure within said envelope, and a plurality of detachable stabilizing fins which are separately inflatable from the main body of the balloon.

In a balloon having a substantially constant volume gas envelope, a substantially non-elastic, light-weight material such as polyethylene is often used for the envelope. Said material is not free to expand or contact as the gas pressure within the envelope increases or decreases while the balloon is aloft. In other words, as the gas pressure within the envelope increases or decreases, the volume of said envelope will undergo little or no corresponding change in size. Means must therefore be provided to prevent the gas envelope from bursting should the internal pressure increase beyond a maximum limit. Such means may include valves for permitting the gas to be valved out of the envelope into the atmosphere as the pressure within the balloon increases beyond a predetermined limit, and wind operated air scoops for forcing air from the atmosphere into a ballonet operatively associated with said envelope, as the pressure within the envelope decreases below the predetermined limit. In some instances, the balloon is reinforced with tapes to aid in maintaining a substantially constant Volume gas envelope; in other instances, a non-extensible shroud is used which surrounds the gas envelope, thereby maintaining a substantially constant volume gas envelope.

Ballonets are often used for maintaining a predetermined pressure within a substantially constant volume balloon. Said ballonets have been found to be instrumental in maintaining the desired shape and size of the outer surface of the balloon. The balloon envelope ordinarily comprises two compartments, one which contains the lifting gas, and the other known as the ballonet, which is filled with air. The ballonet is comprised of an expansible structure which is adapted to expand or contract as the pressure therein increases or decreases. In principle, as the lifting gas within the gas envelope expands, air is forced from the ballonet into the atmos phere, and when the gas contracts, air is pulled or forced into the ballonet by appropriate means, e.g. air scoops. In this way the desired shape and size of the balloon is maintained. Such ballonet principle is known in the art of ballooning, and is not, by itself, a part of this in- Vention.

According to the present state of the art, stabilizing fins are provided to insure stability of the balloon while it is aloft. In some instances the fins are inflated with gas from the envelope, and in other instances said fins are inflated with air from the ballonet. In either case, problems might occur if the fins are in communication with the balloon, i.e., envelope and/ or ballonet. For example, if the internal pressure of the balloon is insufficient, the fins may not be able to retain their shape, and the stability and efficiency of the balloon during flight is reduced, that is, if the fins are inflated with air from the ballonet, an increase of gas pressure within the envelope would force air out of the ballonet and, therefore, the pressure within the fins might be affected.

Another problem which might occur if wind operated air scoops are used occurs when the balloon is in a region of still or calm air. In general, a wind operated air scoop is effective only when there is sufficient wind present to operate it. In substantially still air, the internal pressure of the balloon is such that the air cannot force its way into the balloon. Under such a condition the balloon might become unstable.

Accordingly one object of our invention is to provide an improved light-weight aerodynamically shaped balloon having provisions for maintaining the balloon at a substantially constant volume under all wind conditions.

Another object of our invention is to provide an improved constant volume balloon having a plurality of inflatable stabilizing fins secured thereon which are separately inflatable from the main body of the balloon.

It is another object of our invention to provide a novel means for detachably attaching said fins to the main body of the balloon.

A further object is to provide a pressurization system for maintaining a high internal pressure within the inflatable stabilizing fins of a constant volume balloon regardless of the pressure within the balloon.

A still further object is to provide an improved lightweight aerodynamically shaped balloon having a plurality of stabilizing fins detachably attached to the balloon envelope which are separately inflatable from said balloon envelope.

Another object is to provide a pressurization system whereby a higher internal pressure may be maintained within the stabilizing fins than in the balloon envelope.

A further object is to provide an aerodynamically shaped captive balloon with internal control means for maintaining a predetermined pressure within the balloon envelope, and a plurality of separately inflatable stabilizing fins detachably attached to the balloon envelope.

Other objects and advantages of the invention will become apparent from a consideration of the following specification and accompanying drawings in which:

FIGURE 1 is a side elevational view of a substantially constant volume balloon having an inner gas impervious liner enveloped by a nylon shroud, and a plurality of detachable stabilizing fins attached to said shroud, which are separately inflatable from the main body of the balloon; 7

FIGURE 2 is a rear elevational view of the balloon shown in FIGURE 1;

FIGURE 3 is taken along line 33 of FIGURE 1;

FIGURE 4 is a sectional detailed view taken along line 4-d of FIGURE 1 illustrating the rear end fitting assembly;

FIGURE 5 is a sectional detailed view taken along line 55 of FIGURE 1 illustrating the front end fitting assembly;

FIGURE 6 is an enlarged detailed View illustrating the method of attaching the stabilizing fins in FIGURE 1 to the main body of the balloon;

FIGURE 7 is a sectional View taken along line 7-7 of FIGURE 1;

FIGURE 8 is a sectional view illustrating a typical pressurization system utilized in FIGURE 1;

FIGURE 9 is a detailed view illustrating the manner of attaching the load lines to the balloon of FIGURE 1;

FIGURE 10 is a schematic view of a method of secur ing the inflation tube to a balloon fin, after the balloon has been inflated;

FIGURE 11 is a side elevational view of another embodiment of our invention in which an impervious gas liner is reinforced with a plurality of tapes;

FIGURE 12 is a side elevational view of another embodiment of our invention;

FIGURE 13 is a partial perspective view illustrating the manner of attaching the stabilizing fins to the balloon shown in FIGURE 12;

FIGURE 14 is a perspective view illustrating a further embodiment of one portion of our invention; and

FIGURE 15 illustrates a partial schematic view of the end fitting shown in FIGURE 14.

Referring to FIGURE 1, a substantially constant volume captive balloon It) is shown comprising an aerodynamically shaped inner liner or gas envelope 12, and means for maintaining a substantially constant volume balloon, said means in this embodiment including an outer liner or shroud 14 which prevents the balloon from expanding beyond a predetermined maximum limit. Said balloon is designed to lift heavy loads and to provide stability even when tethered in high winds. Envelope 12 is preferably constructed from a plurality of gores and is adapted to be filled with a lifting gas such as helium. Said gores are formed from a substantially non-elastic gas impervious material such as polyethylene, and are joined together at their respective perimeters to form the inflatable envelope 12. While we have specified polyethylene as the material used to form the envelope, it is apparent that other suitable materials could be used as well. Shroud 14 is also preferably constructed from a plurality of gores which are joined together at their respective perimeters to form a liner which surrounds the gas envelope 12. Said gores are formed from a substantially non-expansible, light-weight material such as a non-expansible nylon fabric. Shroud 14 prevents envelope 12 from tending to expand and consequently burst as the gas pressure within the envelope increases due to ambient temperature changes, ambient pressure changes, and the like. By surrounding envelope 12 with the non-expansible shroud 14, the volume of said envelope 12 will undergo little or no corresponding change in size as the gas pressure therein increases.

Located at the front of the balloon is a front end fitting assembly 22; and located at the rear of the balloon is a rear end fitting assembly 24. Said end fitting assemblies secure the ends of the envelope gores together as well as the ends of the shroud gores together. Said end fittings will be described in greater detail hereinafter.

Located within the envelope 12 is an elongated cylindrically shaped ballonet 16 which also aids in maintaining a substantially constant volume balloon by pressurizing the balloon when the internal gas pressure decreases below a predetermined minimum. Said ballonet is formed of an expansible gas impervious material. As noted in FIG- URE 3 said ballonet is adhesively attached to the bottom surface of envelope 12 along its longitudinal axis (note reference numeral 13). Said ballonet is adapted to ex- Front end fitting 22 is shown in greater detail in FIGURE 5. Envelope 12 is securely attached to one portion of end fitting 22 by tapes 26 and a metallic band 23; shroud 14 is attached in a similar manner to a second portion of said end fitting by tapes 26 and metallic band 28.

FIGURE 4- illustrates a detailed view of rear end fitting 24. Envelope 12 is securely attached to a first portion 36 of said end fitting by tapes 46 and metallic band 48; shroud 14 is securely attached to a second portion 38 of said end fitting in a similar manner by tapes 46 and the band 48.

Inserted within the end fitting 24 is an inflation tube designated generally by reference numeral 30. Inflation tube 36 is comprised of two parts, a tubular metallic cylinder 32 which is inserted within the end fitting 24, and a flexible tube 34 which is attached by tape 46 and metallic band 4-8 to one end of cylinder 32. Tube 34 is comprised of a gas impervious material such as polyethylene. Set screws 44) are provided to secure the end fitting 24 to cylinder 32 and to prevent end fitting 24 from movement relative to the cylinder. As shown in FIGURE 4, a diffuser 4-2 is secured to the second end of the cylinder 32 and is inserted between envelope 12 and end fitting 24. Diffuser 42 is used to aid in proper inflation of the balloon and to prevent injury to the balloon material during inflation. A rubber cement compound 44 aids in maintaining an air tight connection between the end fitting and the interior of the gas envelope.

Located at one apex of the balloon, according to a further feature of our invention, are a plurality of inflatable and detachable fins 50, 52, and 54. Said fins are used to impart aerodynamic and free lift to the balloon, and to stabilize the structure by maintaining the balloon in the proper attitude of flight by preventing the balloon from pitching, rolling and/or yawing. Said fins are secured to the surface of the balloon at 60 and the preferred method of attachment is illustrated in greater detail in FIGURES 6 and 7 and will be described in greater detail hereinafter.

, Balloons with a plurality of stabilizing fins secured to one end are well known in the art. As pointed out hereinbefore, however, said fins are generally inflated with gas from the interior of the gas envelope of the balloon, or if an air inflatable ballonet is used in combination with the gas envelope, said fins are oft times inflated with air from said ballonet. In either case, these methods of inflation may be unsatisfactory because the inflation of the fins depends upon the pressure within the gas envelope or the pressure within the ballonet, and if wind actuated air scoops are used to inflate the ballonet, the pressure within said ballonet, and consequently the fins, depends upon the ambient wind velocity.

In our invention, we provide a first power operated pressurization system 62 for inflating the ballonet, and a second power operated pressurization system 64 for inflating the fins independently of the ballonet or the gas envelope. In other words, the pressure maintained within the fins is independent of the pressure within either the gas envelope or the pressure within the ballonet, and it is possible to attain greater stability by maintaining a higher internal pressure in the fins than that normally required in the gas envelope. Pressurization system 62 is mounted to the lower surface of the balloon, and pressurization system 64 is mounted within stabilizing fin 50. A typical pressurization system is shown in greater detail in FIGURE 8. Said system consists of a centrifugal blower 68 mounted within a light-weight metallic air scoop 72. Said blower is actuated by motor 76 which is electrically connected by wires 80 to a power source 82 suspended beneath the balloon 10. The air scoop 72 is provided with an opening 84 in its forward vertical surface, and an opening 86 on its top horizontal surface. Opening 86 abutts against opening 88 in the lower surface of the balloon, and said opening 88 extends into the ballonet 16. Scoop 72 is attached to the balloon by means of a horizontal flange 83 which is bolted to collar 96, said collar 99 being located between shroud 14 and liner 12.

In operation, blower 68 rotates in a clockwise direction and air is forced into the ballonet. The blower is set so as to put out a desired maximum amount of pressure. If the pressure within the ballonet, or the tail fins, exceeds this maximum amount, air may be valved out through the air scoop itself, or a safety relief valve 94 may be provided to prevent an excessive amount of pressure from being created within the structure 'which is being pressurized.

The fins may be constructed of two layers. An inner gas irnperivous material 58 such as polyethylene, and an outer layer or shroud 56 comprised of a light-weight material such as nylon. Each fin is reinforced by providing a plurality of internal ribs 92 as shown in FIGURE 7. Said ribs add rigidity to the fin and aid in maintaining the proper shape of said fin. The ribs do not extend completely to the forward or rear edges of the fin, therefore, air can flow freely within the fin to completely inflate it.

Frequently aerodynamically shaped captive balloons, such as balloon 10, are extremely large in dimensions, sometimes reaching a length of over 175 feet or more and a diameter of 50 feet or more. We have found that such balloons are difficult to assembly, inflate, service, launch, and the like. To alleviate somewhat the difficulties encountered with such huge balloons, we have provided means for detachably securing the stabilizing fins t 52, and 54 to the main body of the balloon 10. The inner layer 53 of the fin is separately inflatable from the gas envelope 12 of the balloon (note FIGURE 7). The fins are secured at 66 to the main body of the balloon by securing the shroud 56 surrounding the fins to the shroud 14, surrounding the gas envelope 12. A further advantage realized by detachably securing the fins to the balloon is that one or more fins may be replaced if it should become damaged during inflation, while it is aloft or the like.

FIGURE 6 illustrates the preferred manner of attaching the fins to the balloon. As noted in said FIGURE 6, nylon cords 96 and 98 are laced through grommets 106 located in the shroud 58 of fin 5t) and shroud 14. Thus it is seen that the stabilizing fins may be readily detached from the balloon body by unlacing cords 96 and 98 which secure said fins to the balloon body.

Cords 1G2, secured by tabs 164 to the tail fins, are provided to aid in stabilizing the fins and to aid in prevent ing said fins from flopping while balloon It) is aloft and subjected to atmospheric winds.

As noted above, We have provided separate pressurization systems according to the invention for pressurizing ballonet 16 and the tail fins of balloon Ill. In the embodiment illustrated in FIGURE 1, pressurization system 64, which is similar to that described above relative to pressurization systems 62 (note FIGURE 8), is secured to fin 5t}. Fins 52 and 54 are inflatably connected to fin 50 by means of flexible conduits 1% and 108. In operation, air is forced into fin 5G by means of pressurization system 64. Said system includes blowers 66, air scoop 7i and motor 74 electrically connected by wires 78 to power source 32 (note FIGURE 3). As the pressure within fin 59 increases, air is forced into fins 52 and 54 through conduits 106 and 108, respectively.

Power source 82 is suspended beneath the balloon by means of harness cables 11f Cables llltl may be further employed to suspend a load beneath the under surface of the balloon; for example, load ring 12d is provided for attaching a load to the balloon. One method of attaching cables 110 to the balloon is illustrated in FIG- URE 9. Cables 110 are secured to patches 1 14, and adhesively secured webbing strips 11 2 are provided to reinforce the attachment of the cables to said patches. Patches 114 are adhesively secured to shroud 14 and are provided to aid in distributing more uniformly, the forces exerted by the load on the balloon surface.

In operation, gas enevelope 12 of the balloon 10 is inflated with a lifting gas such as helium while the balloon is on the ground. Appropriate means are utilized to maintain the balloon in a position relatively close to the ground to enable the operators to inflate the balloon, service the balloon, and the like prior to its ascent into the atmosphere. After the balloon has been inflated with the desired amount of lifting gas, inflation tube 359 is disconnected from the gas source and the tube is folded inside itself in a manner similar to that disclosed in FIGURE 10 so as to prevent it from dangling and flopping while the balloon is aloft. The tube is then tied shut to prevent leakage of any gas to the atmosphere. As further illustrated in FIGURE 10, tube 34 is provided with tab 116, which is adapted to be secured to tab 118 attached to fin 50. By securing the two tabs together, flopping of the inflation tube 30, while the balloon is aloft, is prevented.

The balloon It in FIGURE 11 is similar to that of FIG- URE l but illustrates a different embodiment of our invention.

In this embodiment, balloon It) is comprised of an aerodynamically shaped gas envelope 12,2 and a plurality of stabilizing fins 124, 126, arid 128 secured to the outer surface of said envelope near one end of said envelope. Envelope 122 is constructed of a plurality of gores which are joined together at their respective perimeters, and is adapted to contain a lifting gas such as helium. Said gores are made of a substantially non-extensible material such as polyethylene. An inflation tube 123 is used to inflate the envelope with the lifting gas. A front end fitting 136 and a rear end fitting 133 are used to connect the ends of the gores together.

Fins 124, 126, and 128 are spaced about the periphery of the tail portion 132 of envelope 122 and are made of a similar material as envelope I22. Said fins may be adhesively attached to the tail portion at 134, or if desired, they may be detachably secured to the gas envelope by appropriate means. For purposes of illustration we have shown them as being adhesively attached to the envelope 122.

As pointed out above, the non-elastic gas envelope 122 might burst as pressure therein increases beyond a certain maximum. In this embodiment the means for maintaining a desired constant or maximum volume balloon includes a plurality of circumferential tapes 140, and a plurality of longitudinal tapes 142 for reinforcing the ba1 loon envelope. Said tapes are adhered to the surface of the envelope 122 and aid in preventing the volume of the envelope from substantially increasing and therefore bursting as the pressure therein increases. Said tapes are comprised of a light-weight, reinforced material and they may be adhesively attached to the envelope surface, heat sealed to said surface, or the like. Said tapes also serve as reinforcing means for attaching a plurality of harness cables 144 to the envelope 12-2. Securing the harness cables to tapes I40 and 142 aids in distributing the load over a larger portion of the envelope surface. A load supporting means 146 is provided for attaching the load to the balloon.

Positioned within the balloon and secured to its bottom surface is an elongated, cylindrically shaped ballonet 148 which is similar to ballonet 15 described in connection with FIGURE 1. Said ballonet 14-8 also aids in maintaining a substantially constant volume balloon by pressurizing the balloon when the pressure therein decreases below a predetermined minimum. Said ballonet is inflated with air by means of a motor actuated pressurization system designated generally by reference numeral 150. Pressurization system 15th is similar to pressurization system 62 described in connection with FIGURE 1 and will not be described in detail.

Fins 124, 126 and 128 are separately inflatable from the gas envelope 122 and/or ballonet 143. Motor actuated pressurization system 152, which is similar to pressurization system 64 described in connection with FIG- URE l, is used to inflate and maintain a desired pressure within the fins. Said system 152 is attached to fin 12d, and fins I26, and 123 are infiatably connected to fin 124 by means of flexible conduits I54 and 156.

Pressurization systems 150 and 152 are electrically connected to power source I57 suspended beneath the envelope 122. We have shown the power source 157 attached to the envelope in a somewhat diflYerent manner than illustrated in connection with FIGURE 1. Ti is manher of attachment is shown merely for illustrative purposes, and if desired said power source could be suspended in a manner similar to that illustrated in FIGURE 1. In balloons of relatively small dimensions, relatively small batteries and the like are required to actuate the pressurization systems. Therefore, it might be desired to merely suspend the power source directly to the envelope as illustrated in FIGURE 11. However, as the balloons increase in size, larger equipment is required to pressurize them. In such instances, the power source may be suspended in a manner illustrated in FIGURE 1 in an effort to distribute the weight over a larger portion of the balloon.

FIGURE 12 illustrates another embodiment wherein the balloon It) is constructed of a uni-wall material rather than a shroud reinforced envelope (note FIGURE 1), or a tape reinforced envelope (note FIGURE ll). Balloons formed according to this embodiment are comprised of an envelope 158 constructed from a plurality of gores which are joined together at their respective perimeters, and a plurality of inflatable and detachable stabilizing fins 160, 162, and 164 attached to its surface. Said gores are formed from a strong, light weight fabric such as nylon, Dacron, or the like, and said fabric in turn is coated with a rubber compound, vinyl compound or the like. Balloons constructed in this manner retain a substantially constant volume regardless of the pressure therein due to the resistance against elongation of the nylon or Dacron elements of the material.

Located within the envelope 158 is a ballonet 166 which is inflatable with air by a motor actuated pressurization system 168. Pressurization system 168 is electrically connected to power source 1'70 suspended beneath the balloon by harness cables 172.

Motor actuated pressurization system 174 is used to inflate and maintain a desired pressure within the fins 16%, 162, and 164 independently of the pressure maintained within the envelope 158 and/or ballonet 166.

Each fin is provided with a first longitudinally extending flap 176 and a second longitudinally extending flap 178. As illustrated in FIG. 13, flap 176 is comprised of a first portion 184) which is adhesively secured to the envelope 158, and a second portion 182, having grommets 184 longitudinally spaced along one edge thereof, which may be angularly disposed relative to the first portion. Flap 178 is comprised of a first portion 186 which is adhesively secured to the fin 16! and a second portion 133, having grommets 15 longitudinally spaced along one edge thereof, which is not adhesively secured to fin I60. Fin 16% is secured to the envelope by lacing nylon cord 192 through grommets 184- and 1%.

Referring to the drawing of FIGURE 14, another embodiment for inflating the fins is illustrated. In this embodiment, fins 1%, 23%, and 2% are simultaneously infiated. Located at the apex of the balloon is an end fitting designated generally by reference numeral 294. Balloon It) is inflated with a lifting 'as through inflation tube 265 which has a diffuser 2% attached to one end (note FIGURE 15).

End fitting 294 has a cavity 215 which is connected to the pressurization system 2% by means of a hollow conduit 220, conduit 228 is located within balloon 1-0. Fins 198, 2th and 2 3 2 are inflatably connected to end fitting 2% by means of conduits 210, 212. and 214, respec- 8 tively. End fitting 294 is attached to the balloon It} by means of tapes 222 and metal band 224-.

In operation, pressurization system 218 is actuated by appropriate motor means and cavity 216 is pressurized through conduit 220. The fins in turn are simultaneously inflated through conduits 210, 212, and 214.

In the embodiments described above, the balloons are provided with an aerodynamically shaped, substantially constant volume gas envelope, which is filled with a lifting gas. Said gas envelope is constructed of a substantially non-elastic, light-weight material which is not free to expand as the gas within the balloon expands thus causing the pressure within the balloon to increase. To prevent the volume of the balloon from expanding and consequently bursting as the pressure therein increases means have been provided to aid in maintaining a substantially constant volume balloon. Said means include a shroud which surrounds the gas envelope, tapes which reinforce the gas envelope, or a gas envelope formed from a uni-wall, reinforced matenial, and an expansible, air inflatable ballonet located within the envelope to compensate for pressure variations within said envelope. Said ballonet is inflatable with air by means of a first motor actuated pressurization system which pressurizes said ballonet independently of ambient wind conditions. Air is forced out of said ballonet as the gas pressure within the gas envelope increases and conversely, as the gas pressure within the gas envelope decreases air is forced into the ballonet by means of the power actuated pressurization system.

Detachably secured to the tail portion of the balloon are a plurality of inflatable stabilizing fins. The pressure within said fins is maintained independently of the pressure maintained Within either the main gas envelope or the ballonet by means of a second motor actuated pressurization system. By inflating the fins independently from the envelope or ballonet with a power actuated pressurization system, said fins will remain pressurized and rigid irrespective of the pressure within the gas envelope, the pressure within the ballonet, or ambient wind conditions. By independently pressurizing said fins, greater balloon stability is achieved while said balloon is aloft.

In the above description and attached drawings, a disclosure of the principles of this invention is presented, together with some of the ways in which the invention may be carried out.

We claim:

1. A balloon comprising in combination an aerodynamically shaped gas envelope, an air inflatable ballonet located within said gas envelope, first pressurizing means for regulating the air pressure within said ballonet, inflatable stabilizing means attached near one end of said gas envelope, and second pressurizing means for inflating said stabilizing means solely with air and for regulating the air pressure within said stabilizing means independently of the pressure within the gas envelope and the hallonet.

2. A balloon comprising in combination a substantially constant volume, ae'rodynarnically shaped gas envelope, said envelope being formed from a gas impervious material, a ballonet located within said envelope, first pressurizing means for maintaining a predetermined air pressure within said ballonet, a plurality of inflatable fins attached near one end of the envelope, said fins being formed a gas impervious material, and second pressurizing means for inflating said fins solely with air and for maintaining a predetermined pressure within said fins independently of the pressure within the gas envelope and the ballonet.

3. A balloon comprising in combination an aerodynamically shaped gas envelope formed from a gas impermeable material, means for maintaining a substantially constant volume balloon, said means including a ballonet located within the envelope and first vpressurizing means for maintaining a predetermined air pressure within said 9 ballonet regardless of ambient Wind conditions, a plurality of inflatable fins attached to the balloon near one end of said balloon, and second pressurizing means for inflating said fins solely with air and for maintaining a predetermined air pressure within the fins independently of the pressure within the gas envelope and the ballonet.

4. The combination of claim 3 wherein the means for maintaining a substantially constant volume balloon also includes a substantially non-extensible shroud at least partially surrounding said envelope, and means for detachably securing the fins to the ballon are provided.

5. The combination of claim 3 wherein the means for maintaining a substantially constant volume balloon also includes a plurality of reinforcing tapes circumferentially spaced around said envelope, and a plurality of reinforcing tapes longitudinally spaced about said envelope. 6. The combination of claim 4 wherein first communicating means are provided for infiatably connecting the first pressurizing means to the ballonet, and second communicating means are provided for inflatably connecting the second pressurizing means to at least one of the inflatable fins.

7. The combination of claim 6 wherein third communieating means are included for inflatably connecting the fins together.

8. A balloon comprising in combination an aerodynamically shaped gas envelope formed from a gas impermeable material, sa-id balloon having a front end fitting, and a rear end fitting, said rear end fitting having a cavity adapted to be pressurized, means for maintaining a substantially constant volume balloon, said means including a ballonet located within the envelope, first pressurizing means for maintaining a predetermined pressure within said ballonet, first communicating means for inflatably connecting said first pressurizing means to the ballonet, a plurality of inflatable fins attached to the balloon near the rear of said balloon, second pressurizing means for maintaining a predetermined pressure within the fins independently of the pressure Within the gas envelope and the ballonet, second communicating means for connecting the second pressurizing means to the cavity in the rear end fitting so that said cavity might be pressurized, and third communicating means for inflatably connecting each fin to the cavity of the rear end fitting.

9. A balloon comprising in combination an elongated, aerodynamically shaped gas envelope, a substantially nonextensible shroud surrounding said gas envelope, an air inflatable ballonet located within said gas envelope, first power operated pressurizing means for maintaining a predetermined air pressure within said ballonet, a plurality of detachable, inflatable stabilizing fins secured to the shroud, and second power operated pressurizing means for maintaining a predetermined air pressure within the fins independently of the pressure within the ballonet, said second pressurizing means inflating said fins solely with arr.

10. The combination of claim 9 wherein the first and second pressurizing means include electrically actuated motors operatively connected to centrifugal blowers.

11. A captive balloon comprising in combination an aerodynamically shaped gas envelope formed from a gas impervious material, said envelope having a front portion and a rear portion, means for maintaining a substantially constant volume balloon, said means including a ballonet within said envelope, first power operated blower means for pressurizing the ballonet regardless of ambient wind conditions, a plurality of inflatable stabilizing fins attached to the balloon, and second power operated blower means for maintaining a predetermined air pressure within said fins independently of the pressure within the gas envelope and ballonet.

12. The combination of claim 11 wherein the stabilizing fins are detachably secured to the captive balloon, and the first and second pressurizing means include electrically actuated motors operatively connected to centrifugal blowers.

13. A captive balloon comprising in combination an elongated, aerodynamically shaped balloon envelope formed of a light-weight, flexible, gas impervious material, said balloon having a front portion and a rear portion, means for inflating said envelope with a lighter than air lifting gas, a ballonet within said envelope, means for pressurizing said ballonet with air when the balloon is airborne regardless of ambient wind conditions, at least one inflatable fin attached near the rear portion of said envelope, said fin being formed from a flexible gas impervious material, and power operated pressurizing means for maintain a predetermined air pressure within the inflatable fin independently of the pressure within the ballonet and the envelope, and regardless of ambient wind conditions.

14. A captive balloon comprising in combination an elongated, aerodynamically shaped balloon envelope formed of a light-weight, flexible, gas impervious, substantially non-elastic material, means for inflating said envelope with a lifting gas, means for maintaining a sub stantially constant volume balloon, said means including a plurality of reinforcing tapes circumferentially spaced around said envelope, a plurality of reinforcing tapes 1ongitudinally spaced about said envelope, and an elongated ballonet within said envelope, said ballonet having a longitudinal axis along which it is secured to the lower inside surface of the ballon, electrically operated pressurizing means in communication with said ballonet for filling said ballonet with air to aid in maintaining a predetermined pressure within said balloon, inflatable fins detachably secure-d to the balloon for stabilizing said balloon while it is aloft and means for filling said fins with air and for maintaining a predetermined air pressure within said fins independently of the air pressure within the ballonet while the balloon is aloft.

15. A light-weight, elongated, aerodynamically shaped, substantially constant volume 'ballon envelope adapted to be filled with a lighter than air lifting gas, an air inflatable ballonet within said balloon envelope, a plurality of separately inflatable stabilizing fins detachably secured to said balloon envelope, said envelope, ballonet, and fins comprising separately inflatable structures, first pressurizing means communicating with said ballonet for pressurizing said ballonet with air, said means including first electrically actuated motor means operatively connected with first blower means, means for attaching said first pressurizing means to the balloon, second pressurizing means communicating with said fins for pressurizing said fins solely with air independently of the pressure within the ballonet, said second pressurizing means including second electrically actuated motor means operatively connected with second blower means, and means for attaching said second pressurizing means to one of said fins.

16. In an aerodynamically shaped balloon formed from a flexible gas impervious envelope, said envelope comprising a plurality of gores joined together at their respective edges, an internal ballonet located within the ballonet and a plurality of inflatable stabilizing fins detaohably secured to the outer surface of the balloon, the improvement including a substantially non-extensible reinforcing means surrounding said envelope to prevent expansion of said envelope beyond a predetermined limit, the balloon having a front end fitting, and a rear end fitting, said end fittings being comprised of two portions, a first portion for connecting the ends of the envelope gores together, and a second portion for connecting the ends of the reinforcing means together, first blower means for pressurizing the ballonet with air, said blower means having an inlet communicating with the outside atmosphere and an outlet communicating with said ballonet, means for connecting said first blower means to the balloon, second blower means for pressurizing the stabilizing fins with air independently of the gas envelope and ballonet, said second blower means having an inlet communicating with the outside atmosphere, and an outlet communicating with at least one of said fins, means for connecting said second blower means to the balloon, and first and second motor means operatively connected to said first and second blower means respectively to actuate said first and second blower means.

17. The combination of claim 16 wherein tubular means are provided for infiatably connecting the stabilizing fins together so that substantially the same internal pressure is maintained in each fin.

References Cited in the file of this patent UNITED STATES PATENTS Gammeter Dec. 3, Smyth Dec. 17, Grifiith Jan. 14, Smyth Apr. 26, Finley Dec. 11, Bradford Apr. 6, Ritter et al. May 12, Winzen et a1 Dec. 29,

FOREIGN PATENTS Great Britain Mar. 3, 

1. A BALLOON COMPRISING IN COMBINATION AN AERODYNAMICALLY SHAPED GAS ENVELOPE, AN AIR INFLATABLE BALLONET LOCATED WITHIN SAID GAS ENVELOPE, FIRST PRESSURIZING MEANS FOR REGULATING THE AIR PRESSURE WITHIN SAID BALLONET, INFLATABLE STABILIZING MEANS ATTACHED NEAR ONE END OF SAID GAS ENVELOPE, AND SECOND PRESSURIZING MEANS FOR INFLATING SAID STABILIZING MEANS SOLELY WITH AIR AND FOR REGULATING THE AIR PRESSURE WITHIN SAID STABILIZING MEANS INDEPENDENTLY OF THE PRESSURE WITHIN THE GAS ENVELOPE AND THE BALLONET. 